javascript 檢查IP正確性

function checkIP(ip){
var re = /^((\d)|(([1-9])\d)|(1\d\d)|(2(([0-4]\d)|5([0-5]))))\.((\d)|(([1-9])\d)|(1\d\d)|(2(([0-4]\d)|5([0-5]))))\.((\d)|(([1-9])\d)|(1\d\d)|(2(([0-4]\d)|5([0-5]))))\.((\d)|(([1-9])\d)|(1\d\d)|(2(([0-4]\d)|5([0-5]))))$/;

if(re.test(ip))
return true;
else
return false;
}